Electric fuse



Sept. 29, 1936. o. H. .JUNG ET AL ELECTRIC FUSE Filed July l, 1932 2Sheecs--Sheefl l Sept. 29, 1936. o. H. JUNG ET AL ELECTRIC FUSE FiledJuly l, 1932 2 Sheets-Sheet 2 Patented Sept. 29, 1936 UNITED STATESELECTRIC FUSE Oscar H. Jung and Paul E. Hefelfinger, Milwaukee, Wis.

Application July 1, 1932, Serial No. 620,372

9 Claims.

This invention pertains to electric fuses, and more particularly -to afusible link utilized in electric circuits to protect the same from theeffects -of .momentary excessive current.

Itis well-known that the starting current of all motors manufactured atthe present time varies 4considerably between wide limits. Due to thischaracteristic, all fuse links used at the present time are notladaptable to Vthe starting current, or characteristics yof varioustypes of conventional motors. Because of this lexisting condition, motor`circuits must 4be over-fused, and therefore do :not Thave 100% fuseprotection.

Conventional fuse links in use at the present time Vmake provision *foravtime lag inthe fusing period of .the link .to prevent overload of briefduration from fusing `the link, as for instance, when an alternatingcurrent motor is thrown into the line. This is accomplished by soproportioning certain parts of .the link as to absorb suflicient .heatto-delay the .period of fusing until such time as .the normal operationof the motor reduces the current lto its normal stage. Such fuse linksare satisfactory only insofar as the amount of excessive current:generated is predetermined, and in instances where additional loads or.motors are connected in the line, the fuse links must necessarily bechanged to compensate for various time lags in order to Vpreventpremature fusing, This requires a large stock of fuses to vbe kept onhand for frequent changing.

The .present invention has .primarily for its object to overcome theforegoing objections by the provision of a fuse link designed tonormally fuse at a predetermined load and provided with means forregulating the fusing period to compensate for various initial excessiveoverloads.

Incidental to the foregoing, a more specific object of the presentinvention resides in providing a fusible link with shiftable metallic ornonmetallic members, whereby the period of fusing may be reduced orincreased as desired.

Another object of the invention results from the ability to cause thefusible link to selectively fuse at either one point in the link or atspaced points, the latter being sometimes desirable to cause asubstantial portion of the link to drop out upon fusing, thus preventingsubsequent arcing.

With the above and other objects in view, which will appear as thedescription proceeds, the invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more parpractical application of the principles thereof.lll;

In the drawings, Figure 1 is an elevation of a conventional type of fuselink with the Apresent invention applied thereto;

Figure 2 is an end elevation;

Figures 3, 5, '7, 9, 1-1, 13 and 15, are elevational 15` views ofmodified forms of the invention;

Figure 4 is an end elevation of the form shown in Figure 3;

Figure 6 is an end elevation of the form shown in Figure 5;

Figure 8 is an end elevation of the form shown in Figure 7;

Figure V1'0 is an end elevation of the form shown in Figure 9.;

Figure 1.2 is a transverse section taken on the line I2-|2 of Figure 11;and

Figure 14 is a transverse section taken on the line l4-l4 of Figure 13.

Referring now more particularly to the accompanying drawings, whereinthe fusible strips of the various forms illustrated are designated bythe numeral l, the same are provided adjacent their ends with transverseslots 2 for attachment to suitable terminals, not shown, it beingunderstood that the invention can be applied to any 3. type of fusiblestrip, although the same is most applicable to what are commonly termedrenewable links.

Referring to the structure shown in Figures 1 and 2, the link I, formedof fusible metal, is pro- 40 vided with an elongated longitudinal slot3, which serves to .provide restricted intermediate portions 4, whereinthe fusing occurs as the link becomes heated through excessive current.

The link thus far described is conventional, 4.5 and as heretoforeexplained, under ordinary conditions when the same is subjected toinitial excessive current, the link would quickly fuse to break thecircuit, although the excessive current may be present for only a briefperiod in starting a, motor or similar devices. Therefore, in -order toincrease the period of fusing of the restricted portions 4, to thusprovide a time lag, the strip or link I is provided with shiftable metalclips 5, the ends of which are folded over the link to retain the clipsthereon and provide for longitudinal shifting of the same.

In normal use of the fuse, the clips 5 are positioned adjacent theextremities of the link and thus have little or no effect upon theintermediate restricted portions fi, inasmuch as they are suicientlyspaced therefrom as to absorb practically no heat from those portions.Therefore, the restricted portions Il will quickly fuse at apredetermined current.

In order to increase the period of fusing,rit is merely necessary toshift the clips 5 toward each other, and naturally as they approach thecentral or intermediate part of the restricted portions ll, they willabsorb heat therefromand thus increase the period of fusing. Inthe eventthat the clips are shifted toward the center of the link intolengagement with each other, as shown in dotted lines in Figure 1, itwill be quite obviousthat they will act to absorb heat from the centralarea of the restricted portions, thus causing "the restricted portionsto fuse in two places upon opposite sides of the clips, resulting in theintermediate portions dropping out to provide a substantial gap whicheliminates any possibility of arcing.Y

From the foregoing explanation, it will be quite apparent thatexceedingly simple and inexpensive means has been provided for varyingthe periodof fusing of the link and for selectively causing the link tobe fused either at an intermediate portion or at spaced portions.

As heretofore explained, it is old and Wellknown to either proportioncertain portions of a link so as to provide a time lag, or to accomplishtheV same by adding metallic plates for the purpose of absorbing heatfrom the fusible portion of the link. However, such links do not providefor varying the fusing period, and therefore frequent changes .and alarge stock of links are required.

Obviously, thepresent invention overcomes .the foregoing and pro-videsfor considerable variation in the period of fusing within a substantialrange, thus enabling a singlelink Vto be readily accommodated to variousconditions, and also enabling the link to be readily converted from aconventional fuse linkA to what is commonly termed a drop-out. link. Y

Referring to Figure 3, the link I is provided with spaced restrictedportions and an intermediate restricted portion 1 of lesscross-sectional area than the restricted portion 6. Normally, such linkwould fuse at the intermediate portion 1 and by shifting the clips 5,the period of fusing can be varied, as heretofore explained.. In theevent that the clips V5 are shifted to engage each other, as shown indotted lines, then the link I will fuse at the restricted portion 6,causing the intermediate portion of the link to drop out.

The link shownrin Figure 5 is a conventional drop-out link provided withonly two spaced restricted portions 8. In this form, when the clipsV 5are shifted to central position, as shown, they will have little or noeffect in absorbing heat from the restricted portions, and therefore thelink will fuse in a minimum period of time. However, by shifting theclips apart to the position indicated in dotted lines, they wouldthenserve to absorb heat from the restricted portions and V increase thefusing period.

sertion in the spaced recesses II, and reception of nuts I2 to securethe buttons to the link. Ob-

viously, any other suitable form ofY attachmentV may be utilized, theessential feature of the structure residing in the shiftability of themetallic buttons to effect the absorption of heat from the fusibleportion of the link, thus varying the period of fusing.

In the form illustrated in Figures 13 and 14, instead of slidable orshiftable metallic members, the link I is provided with either one ortwo rotatable metallic plates I3, pivotally secured to the link uponopposite sides of the restricted intermediate portion 1. In order toinsure proper contact between the rotatable plates I3 and the link I,lips Mare preferably provided for engagement with the plates, the lipsbeing formed out of the body of the link.

fuse Within the minimum predetermined period.

However, by rotating the plates I3 across the restricted portion, thesame will absorb sufficient heat from the restricted portion to prolongthe period of fusing, and inasmuch as the platesV I3 are flared fromtheir free ends, the period of fusing can be varied to a high degree ofnicety.

In Figure 15, a single slidable plate I5 is provided, held in slidingengagement with the link I, by means of the lips. I6 bent over from theopposite longitudinal edges of the link into engagement with the plateI5. As will be noted, the plate I5 is provided with an intermediaterestricted portion I1 conforming to the restricted portion 1 in thelink.

In operation, when the plate I5 is shifted to that position illustrated,heat will be dissipated from the restricted portion 1 and absorbed bythe plate .|5 to provide for a maximum period of fusing. When shifted inthe opposite direction, so that the restricted portions 1 and I1 arealigned, the portions 1 and I1 will fuse in the minimum period of time.r

In the forms shown in both Figures 13 and V175, obviously when themetallic plates are shifted to provide a greater cross-sectional area atthe central portion of the links than at the ends,

the links will fuse at the ends, causingV Vthe intermediate portion todrop out, as heretofore explained.

Thus, in all forms of the invention described, both salient features arepresent, namely, the ability to vary the period of fusing or selectivelycause the link to fuse at an intermediate portion, or Vat spaced points,causing the intermediate portion to drop out, relieving strain upon therestricted portions of the link, thus eliminating objectionablestretching and centering of the link, and, in instances where more thanone link is bolted across Ythe terminals or blades, to cause theunrestricted portions of the links to be bent outwardly or away fromeach other, thus increasing the distance between the two points andrendering arcing more difIicult.

Having thus illustrated and described the invention in considerabledetail, it is to be understood that various modifications arecontemplated as coming within the scope of the same.

We claim:

1. A fuse link comprising a fusible strip for connecting a pair ofelectric terminals, and movable means carried by said strip for varyingthe fusible period of said strip.

2. A fuse link comprising a fusible strip for connecting a pair ofelectric terminals, and movable means carried by said strip forabsorbing heat from desired portions thereof.

3. A fuse link comprising a fusible link for connecting a pair ofelectric terminals, a pair ol movable members carried by said strip forabsorbing heat from certain portions of said strip to vary the fusibleperiod of said portions.

4. A fuse link comprising a fusible strip for connecting a pair ofelectric terminals and provided With a contracted fusible portion, apair o1 movable members carried by said strip for affecting thedissipation of heat from said restricted portions to vary the fusibleperiod of said portions.

5. A fusible link comprising a. fusible strip for connecting a pair ofterminals, a pair of slidable heat dissipating members carried by saidstrip for adjustment toward or away from each other.

6. A fusible link comprising a, fusible strip for connecting a pair ofelectric terminals, and means carried by said strip for selectivelycausing the same to fuse at either one or two places.

7. A fuse link comprising a fusible strip for connecting a pair ofelectric terminals, and movable means carried by said strip forselectively causing the same to fuse at an intermediate portion or atspaced portions.

8. A fuse link comprising a fusible strip for connecting a pair ofelectric terminals, and means carried by said strip for varying thefusible period of said strip, and selectively causing said strip to fuseat either one or two places.

9. A fuse link comprising a fusible strip for connecting a pair ofelectric terminals, and a pair of metallic clips engaging said strip forslidable movement thereon to vary the fusible period of said strip.

OSCAR H. JUNG. PAUL E. HEFFELFINGER.

